F I S K E R P D P R E K T O R A T E T S S X R I F T E R S E R I E N A V U N D E R S B K E L S E R Retorts on Norwegian Fishery and Marine Investigations
Vol. 13, No. 4, I962
A Pressure Aquarium for Experimental Use
BY
G U N N A R S U N D N E S
Fiskeridirektoratets Havforskllingsinstitutt
B E R G E N 1 9 6 2
I n experiillental aquatic science the hydrostatic pressure is fre- quently a point of interest. I n the past most studies have been carried out under natural conditions a t the appropriate depths. While some aquaria have been constructed for use a t increased pressures, the criteria of constant pressure of the dissolved gases, continuous flow of water through the vessel, constant hydrostatic pressure and a noncavitating pump system have not been met.
Fig. 1 shows a simple pressure aquarium designed by the author.
I t is constructed of stainless steel and has a volume of 360 liters.
I n order to increase the pressure resistance without unduly adding to the weight of the aquarium, five steel rings (1 X I") are fitted around the 5 mm thick stainless steel pressure tank as shown in Fig. 2.
T h e water pressure is produced by a 1" centrifugal pump fed by water a t a pressure of five meters. 'The pressure valve at the outlet contains a series of springs which allow for a continuous pressure varia- tion from 0-100 meters to be made.
A
safety valve opens if the pres- sure exceeds 100 meters. T h e side of the aquarium has two windows made of double layers of glass measuring 36 mm in total thickness. One of the windows is used for lighting and the other for observation. T h e opening a t the top is closed by a n inside fitting cover to prevent leakage a t high pressure. There is a water - and pressui-e-tight connection for wires connected to measuring units within the aquarium.Due to the nature of the biological probleins to be studied, no super- saturation of gases in the water was allowable. As it was possible that some cavitation could occur in the pump and thereby cause supersatura- tion, a series of oxygen analyses were made a t controlled tempera- tures and salinities. It was found that, by supplying the pump with water a t a pressure of five meters, no supersaturation of the water in the
Figure 1. Picture of the pressure aquarium.
aquarium took place. Fig. 3 shows the oxygen saturation of the aquarium water plotted against the "depthJ'i.e. pressure.
T h e water through-flow and its relation to the "depth" in the aqua- rium is also of importance as it limits the size or riuinber of the animals that can be maintained in the tank. In Fig. 4 the values for the minute volume are plotted against "depth". These flow-through rates allow for aniinals weighing up to 2 Icg to be kept in the aquari~lin at pressures cor- responding to a depth of 100 ineters (Sundnes 1957).
From the data that has been obtained it seems, therefore, that this aquarium reproduces the conditions in the sea at the pressures that can be produced, except for the factor of space.
T h e pressure aquarium has made it possible for a number of physi- ological experiments to be carried out at 100 ineters "depth". T h e func- tion of the swiinbladder and einbolic diseases have been investigated.
T h e activity of the heart and the rnouth-g-ill ventilation in relation to
"depth" have also been studied. In Fig. 5 electrocardiograms a r e shown from a cod (Gadzcs callarias
L.)
at 3 and 100 meters "depths". From the diagrams the frequency of the heart beats and the mouth-gill ventila- tion can be seen. T h e results indicate that these functions are seemingly independent of the hydrostatic pressure.Figure 2. Construction drawings of the pressure aquarium.
A - air outlet, S - safety valve, opellillg a t 10 atm. M - manometer, V - vari- able pressure valve, 0 - outlet, SR - steel ritlgs, G - glass x\~indox\rs, P - pump, D - draiiiillg valve, R C recorder contact, K - cover, M H - opening into tank, T\'F - ~ \ l i n d o ~ ~ ~ frame of 35 X 35 luln steel.
DEPTH IN METERS
Figure 3. T h e oxygen content i n the aquarium in relation to "depthy' 14 l6 i I t t ,
18 20 22 24 26 28
i.e. pressure. t = 8.8"C, S O/,, = 34,76. o t = 9.5"C S O/,, = 34.79
LITERS PER MINUTE *
Figure 4. T h e minute volume of the through-flow in relation to o,
l
"depth" i.e. pressure. l
Figure 5. A - electrocardiogram from a cod (Gadus callarias) a t a "depth" of 3 meters.
B - electrocardiogram [rom the same fis11 at a "depth" of 100 meters. V - one inouth- gi11 ventilation cycle. T h r vertical arrows shows heart beats.
I am greatly indebted to
Mr.
0 . Iversen, University of Oslo, for technical collaboration and to the workshop of Dalssren-0degaard &Co. T h e construction of the pressure aquarium was made possible by a grant from Fiskerin~ringens Forssksfond.
L I T E R A T U R E C I T E D
Sundnes, G., 1957. Notes on the energy nletabolisln of the cod (Gadus callarias L.) aild the coalfish ( G a d u s wirens L.) in relation to body size. Fiskeridir. Skr. Ser. H a u - ztnders. 11 (9): 1-10.
